1. Field of the Invention
The present invention relates to an online character recognition system for use in pen-inputting-capable electronic equipment for recognizing input characters online by using standard strokes which are obtained in advance by the quantization of strokes of a character to be recognized.
2. Description of the Related Art
Pen-inputting-capable electronic equipment such as an electronic note, a pen computer or the like includes an online character recognition system for conducting online recognition of characters input through a handwritten character input device. One of conventional online character recognition systems of this kind is disclosed in Japanese Patent Laying Open (Kokai) No. Heisei 5-38351, entitled "Online Character Recognition System" (Reference Literature 1).
In the online character recognition system recited in this literature, strokes of a character to be recognized (lines of strokes made from pen-down to pen-up) are quantized to generate representative strokes (hereinafter referred to as standard strokes) which are stored in standard stroke storing means. A character dictionary for use in recognizing characters stores a category to be recognized and a string of numbers allotted to standard strokes (hereinafter referred to as a standard stroke number-string) constituting a character in the category. In the character dictionary, when the order of making strokes in a character is fixed, the numbers of the standard stroke number-string allotted to the standard strokes are arranged in the order of making strokes.
In such an online character recognition system as described above, upon input of a character through a pen-inputting device, an inter-stroke distance is first calculated between each stroke of the input character and every standard stroke stored in a standard stroke storing means and is stored in an inter-stroke distance table. Inter-stroke distance here represents a displacement of a stroke of an input character from a predetermined standard stroke which are superposed with each other as a value of a distance.
Next, with respect to a category having the same number of strokes as that of the input character out of the categories stored in the character dictionary, an inter-stroke distance between the n-th (n=1, . . . , N; N: the number of strokes of a character) standard stroke and the n-th stroke of the input character is taken from the distance table. With a sum of all the inter-stroke distances from n=1 to n=N as an inter-character distance, a category that provides the minimum inter-character distance is output as a recognition result.
Such character recognition method using standard strokes in most cases enables reduction of the amount of operation required for character recognition. With 200 characters of 10 strokes to be recognized, for example, calculation of inter-stroke distances in all the characters without using standard strokes should be conducted 2000 times (=10 strokes.times.200 characters). On the other hand, in the character recognition method recited in the above literature, assuming standard strokes to be of 20 kinds, calculation of inter-stroke distances should be conducted only 200 times (=10 strokes.times.20 kinds).
The above-mentioned conventional character recognition method using standard strokes, however, has the following shortcomings.
First is that the amount of operation can not always be less than that by a method employing no standard stroke and that the amount of operation is increased in a particular case where standard strokes are of many kinds and characters to be recognized are of a small number of kinds. This is because an inter-stroke distance is obtained between each stroke of an input character and every standard stroke.
Assuming standard strokes to be of 200 kinds, for example, the character recognition method set forth in the above-described literature requires 2000 times (=10 strokes.times.200 kinds) of inter-stroke distance calculations, making no reduction in the amount of operation. Moreover, with 100 characters of 5 strokes and 200 kinds of standard strokes, calculation of an inter-stroke distance is required 500 times (=5 strokes.times.100 characters) when no standard stroke is used. When standard strokes are used, 1000 times (=5 strokes.times.200 kinds) of inter-stroke distance calculations are necessary to increase the amount of operation.
Second is that enormous working memory capacity is required because every calculated inter-stroke distance is stored in an inter-stroke distance table on a working memory.